Vocabulary acquisition is a crucial contributor to the development of fluent signed communication skills and the acquisition of English reading and writing in deaf students. Yet almost all of the existing research has focused on describing the limitations of their vocabulary achievements, and little is known about the process by which deaf children naturally acquire-vocabulary and the variables that influence and constrain that process. Most of the spoken and written English vocabulary of normally-hearing children is acquired rapidly and incidentally from exposure to new words in conversational discourse and written text. Extensive research has documented the nature of this process and factors that influence it in normally-hearing children, but in the case of deaf children it is poorly understood. The proposed research investigates the way deaf students map meanings onto new words that they encounter in signed discourse input (both in American Sign Language and in the Signed English used in their educational settings) and in the reading of extended English text. Several experiments will examine variables that may affect deaf students ability to acquire new English vocabulary from paragraphs of text: (1) reading comprehension skills and strategies; (2) informativeness and types of semantic and syntactic clues to word meaning in the text passages; (3) concreteness and grammatical form class of the new words; and (4) the use of successive contexts to delimit the possible meanings of an unknown word. Further studies on written English will develop and test classroom techniques for direct instruction in how to use context clues to meaning, in order to facilitate this learning process in deaf students. Finally, two experiments will investigate factors that determine the ability of deaf students to acquire new sign vocabulary from ASL or Signed English narratives that accompany videotaped cartoon stories. ASL is progressively being introduced into deaf children's education, mostly in the form of ASL storytelling, but we have no evaluation of how well students at different ages and with different existing language skills acquire new signing vocabulary from such an input. The proposed research will provide a better understanding of the natural process of vocabulary development that is essential for more effective language intervention.